||Thermal Performance Analysis of Vapor Chamber Applying on Multiple Heat Sources
||Department of Mechanical and Electro-Mechanical Engineering
Multiple Heat Sources
Spreading Thermal Resistance
|| The objective of this thesis is to compute the spreading thermal resistance of multiple heat sources on a vapor chamber module, as well as the surface temperatures and the heat flux distributions at the heating surface. The analytical correlations are expressed in a dimensionless with the governing parameters of the relative distance dimensions between heat sources and dimensionless heat sources size on heat spreader, including a vapor chamber and metal materials evaluation, subject to the influence of multiple heat sources. This study also presents vapor chamber temperature distribution on heat spreader contact surface, and it correlates to heat sources number and distance. Hence, spreading thermal resistance decreases with the increasing lateral length of vapor chamber. There is large difference between spreading and conductive thermal resistance as lateral length is disproportion to heat source heating area. Therefore, spreading thermal resistance is an important factor when design the thermal solution of a high density chipset power, and it caused high temperature in heat sources which embedded a thinner heatsink base, especially. Spreading thermal resistance is disproportion to heat spreader size, material conductivity, then conductive thermal resistance is not the only parameter for vapor chamber module design, it needs to consider the spreading resistance effect of a vapor chamber and multiple heat sources array, Bi number can be fairly understood by imagining the heat flow from small and hot heat sources suddenly immersed in a pool, to the surrounding fluid. Numerical simulation results of the integrated vapor chamber module are carried out with the mathematical model. The computed results are in good agreement with the experiments, and deliver a difference of 3.3% for the maximum heat source temperature rises, and it presents predictable thermal phenomena of a vapor chamber applying on multiple heat sources.
||Table of Content
Title Page II
Signature page III
Abstract (Chinese) V
Abstract (English) VII
Table of Content IX
List of Figure XII
List of Table XVIII
Chapter 1 Introduction 1
1.1 Motivation for research 3
1.2 Literature review 5
Chapter 2 Multiple heat sources in electronics cooling 13
2.1 Heat generating in electronics and present applications 13
2.2 Current cooling technologies 15
2.3 Roadmap for cooling in high power electronics 17
2.4 Manufacture processes of vapor chamber 19
2.4.1 Heat transport limitations 21
2.4.2 Vapor chamber dynamics 22
2.4.3 The working fluid 24
2.4.4 The wick structure 26
Chapter 3 Formula and solution 29
3.1 Spreading thermal resistance 30
3.2 Base thickness design of a vapor chamber 33
3.3 Fins 35
3.3.1 Fin design parameters 36
3.3.2 Suggestions of fin design 40
3.4 Biot number 40
3.5 Temperature equation 41
3.6 General equation of multiple heat sources 45
3.6.1 Multiple heat sources in circular array 48
3.6.2 Multiple heat sources in matrix array 51
Chapter 4 Experiment 56
4.1 Experimental setup and calibration 56
4.2 Experiment results of dual resources (natural convection) 59
4.3 Thermal resistance measurement for VC performance validation (liquid cooling) 64
4.3.1 Test conditions 64
4.3.2 Test equipment of liquid cooling 64
4.3.3 Thermocouple locations 65
4.3.4 Definition of thermal resistance 66
4.3.5 Test data 66
4.3.4 Definition of thermal resistance 66
4.4 Thermal resistance measurement (wind tunnel) 67
4.5 Experiment setup of quad heat sources (LED natural cooling) 71
Chapter 5 Numerical ayalysis 77
5.1 Overview of thermal modeling in electronics cooling 77
5.2 Simulation setup 79
5.3 Modeling 80
5.4 Fin optimization by simulation 82
5.5 Numerical analysis referred to experimental data 84
5.6 Vapor chamber application on multiple heat sources cooling 91
5.7 Contour plot of response surface optimization 95
5.8 Error correction 99
5.9 Uncertainty analysis 100
Chapter 6 Conclusion and future work 103
6.1 Conclusion 103
6.1.1 Design an optimal geometry heat spreader for multiple heat sources cooling 104
6.1.2 Analysis thermal phenomena of multiple heat sources heat spreading on a vapor chamber 104
6.2 Future work 106
Appendix I Introduction of linear regrssion method 115
Appendix II Thermocouple calibration 120
Appendix III Thermal conductivity of material property 121
Appendix IV Vapor chamber orientation test data 122
Appendix V Reliabilitytest of a vapor chamber 125
Publication list 132
List of Figures
Fig.1.1 Experiment result of thermal resistance and air volume flow 3
Fig.1.2 Heat dissipation path of a chipset package 4
Fig.1.3 The design range by using a vapor chamber to a metal heatsink. 5
Fig.1.4 Illustration of heat flux spreading in base 6
Fig.1.5 Dimensionless geometry variation to heat source temperature 6
Fig.1.6 Temperature map of source plane for heatsink 7
Fig.1.7 Thermal resistance difference by spreader sizes 8
Fig.1.8 Surface temperature distribution at copper base plate thickness of 5mm 9
Fig.1.9 Maximum temperature location at aluminum heatsink base 10
Fig.1.10 Correlation factor to heat source location 10
Fig.1.11 Quad heat sources dimension definition 11
Fig.1.12 Equivalent heat source and thermal resistance with heat source size 12
Fig.1.13 Equivalent heat source and thermal resistance with heat source location 12
Fig.2.1 Chipset array on a print circuit board 14
Fig.2.2 LED array for lighting applications 14
Fig.2.3 Different shapes of vapor chambers 15
Fig.2.4 System on chip power consumption trends 17
Fig.2.5 Vapor chamber configuration 20
Fig.2.6 Vapor chamber manufacture processes 20
Fig.2.7 General working behavior of a vapor chamber 21
Fig.2.8 An operating cycle diagram of a vapor chamber 23
Fig.2.9 Flow chart of a vapor chamber operating phenomena 24
Fig.2.10 Microscope picture of sintered particles 27
Fig.2.11 Sintered wick structure of a vapor chamber 28
Fig.3.1 Schematic diagram of the square base spreader 29
Fig.3.2 Heat source with temperature distribution on a heatsink 31
Fig.3.3 Temperature profiles at the surface of aluminum extrusion 32
Fig.3.4 Temperature profiles at the surface of extrusion with vapor chamber 32
Fig.3.5 Thermal resistance network 33
Fig.3.6 Block resistance with base thickness of the fin attached spreader 34
Fig.3.7 Heat spreader thermal resistance with base thickness 35
Fig.3.8 Fin types by various manufacture processes 36
Fig.3.9 Sketch of fin parameters 37
Fig.3.10 Heat spreader with dual heat sources 42
Fig.3.11 Heat sources locations on heat spreader 42
Fig.3.12 Thermal resistance network of dual heat sources 43
Fig.3.13 Top surface temperature distribution of dual heat sources by Muzychka et al.'s solution 44
Fig.3.14 Top surface temperature distribution of dual heat sources by Yun Ho Kim a, et al.’s solution 44
Fig.3.15 Thermal spreading resistances vs. heat flux 45
Fig.3.16 Flow chart of multiple heat sources design target 46
Fig.3.17 Calculate multiple heat sources from equivalent heat source 47
Fig.3.18 Methodology of multiple heat sources to an equivalent heat source 48
Fig.3.19 Description of multiple heat sources in circular array 49
Fig.3.20 Dimensionless size of a single equivalent heat source 51
Fig.3.21 Multiple heat sources in matrix array 52
Fig.3.22 Zoom in the multiple heat sources in matrix array 52
Fig.3.23 Temperature distribution of matrix array heat sources on heat spreader 54
Fig.3.24 Correlation of equivalent heat source with dimensionless heat source size of heat spreaders 55
Fig.4.1 Thermocouple measured locations 56
Fig.4.2 Experiment equipment description 58
Fig.4.3 Sketch of test piece measured points 58
Fig.4.4 Vapor chamber structure embedded on a heatsink base 59
Fig.4.5 Application of vapor chamber (Lower spreading resistance) 61
Fig.4.6 Aluminum heatsink (Higher spreading resistance) 61
Fig.4.7 Temperature difference comparison of various ambient 62
Fig.4.8 Temperature description of different fin efficiency 63
Fig.4.9 Thermal resistance comparison of various ambient 63
Fig.4.10 Test platform of liquid cooling 64
Fig.4.11 Test piece description 65
Fig.4.12 Thermocouple location on vapor chamber 65
Fig.4.13 Cooling surface area of vapor chamber 65
Fig.4.14 IR Picture for surface temperature difference comparison 67
Fig.4.15 Air flow direction of test piece 68
Fig.4.16 Wind tunnel for providing system flow and impedance 68
Fig.4.17 Thermal test platform with wind tunnel 69
Fig.4.18 Comparison thermal resistance with vapor chamber and blocked by input power 69
Fig.4.19 Test procedures from heat sources distance 20mm to 50mm 71
Fig.4.20 Test methodology and equipment (natural convection with fin) 72
Fig.4.21 Natural convection chamber 72
Fig.4.22 Reliability of a cool white LED luminous flux efficiency 73
Fig.4.23 Correlation concept of multiple heat sources and equivalent heat source 74
Fig.4.24 Temperature measured point of equivalent heat source 75
Fig.4.25 Test configuration of an equivalent heat source 76
Fig.5.1 Finite difference method for system modeling 78
Fig.5.2 Simulation processes flow chart 80
Fig.5.3 Finite element location design range by minimizing Tjuncton temperature of dual heat sources 82
Fig.5.4 Configuration of a vapor chamber embedded on plat fin heatsink 82
Fig.5.5 Sggested fan-less thermal solution for 4W 83
Fig.5.6 Suggested fan-less thermal solution for 7W 83
Fig.5.7 Design range of fin number 50~60 84
Fig.5.8 Conductivity comparison with vapor chamber and copper plate by increasing input power 86
Fig.5.8 Contour plot of temperature distribution with heat source on a spreader corner 86
Fig.5.9 Material conductivity to thermal resistance by multiple heat sources 87
Fig.5.10 Heat sources temperature by varying power input of multiple heat sources number 87
Fig.5.11 Percentage of spreading thermal resistance on the total thermal resistance by different heat spreader materials 88
Fig.5.12 Dimensionless spreading thermal resistance varies with the distance (h=100) 89
Fig.5.13 Spreading thermal resistance of heat spreaders by multiple heat sources and dimensionless heat source pitch 90
Fig.5.14 Experiment data comparison with numerical result 91
Fig.5.15 Thermal resistance of various dimensionless heat source size and distance (h=100 W/m2C) 92
Fig.5.16 Total thermal resistance vs. convection coefficient (m/l= 0.167) 92
Fig.5.17 Heat conduction inside the body is much faster than the heat conduction away from its surface (m/l= 0.167) 93
Fig.5.18 Thermal resistance compare with Bi number by dimensionless distance (m/l= 0.167) 94
Fig.5.19 Optimal design domain calculated by spreading resistance and dimensionless heat source area 95
Fig.5.20 Optimal response surface temperature of a vapor chamber (d/l=0.25) 96
Fig.5.21 Optimal response surface temperature of a vapor chamber (d/l=0.4) 97
Fig.5.22 Surface temperature distribution along lateral length of a vapor chamber (Thickness = 3.5mm, h>500 W/m2K) 98
Fig.5.23 Optimal design domain with base thickness and convection coefficient of a vapor chamber 98
Fig.6.1 Concept of advanced vapor chamber heatsink design 106
List of Tables
Table 2.1 Maximum power dissipation of 0.98W/mm2 for a single chip by 2013 18
Table 2.2 Thermal spec of system performance requirement 19
Table 2.3 Properties of considered liquids 25
Table 3.1 Base thickness design range by different materials 35
Table 3.2 Correlation factor of equivalent heat source in circular array. 50
Table 3.3 Correlation factor of equivalent heat source in matrix array 53
Table 4.1 T-type thermocouple calibration data 57
Table 4.2 Temperature differences on various fin orientation and contact wall materials 60
Table 4.3 Experiment data of vapor chamber by liquid cooling 64
Table 4.4 Test data of thermal resistance by liquid cooling 66
Table 4.5 Experiment data of vapor chamber heatsink (wind tunnel) 67
Table 4.6 Thermal resistance measured data of vapor chamber 70
Table 4.7 Vapor chamber application on LED cooling (natural convection) 71
Table 4.8 Cree cool white LED thermal spec and reliability 73
Table 4.9 DOE Energy Star strategy for solid-state lighting general illumination products establishes a transitional approach 73
Table 4.10 Experimental scenarios of quad heat sources thermal test data 74
Table 4.11 Test data of equivalent heat source 76
Table 5.1 Material properties of simulation models setup 85
Table 5.2 Simulation data of vapor chamber 91
Table 5.3 Experimental error and calculated uncertainty data 102
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